NEVER DONE A BAT!???!
I don't know if you know the protocol, so here it is:
Fast for 12 hours (overnight). Dr. Center has now said they don't need to fast for this long but it is okay to do and is most popular.
Draw blood.
Give either a regular meal or a high fat meal (different vets do different things...sometimes they use canned A/D).
Wait 2 hours.
Draw blood again.
Send to lab.
Get results in 1-3 days.